Add logs support on Kafka exporter

[sincejune]

Description:
Add logs support on Kafka exporter

Link to tracking Issue:
Related to #1331
Related to open-telemetry/opentelemetry-collector-contrib#268

Testing:

• Added corresponding unit tests according to traces and metrics.
• Tested locally with Kafka 2.11-2.0.0

Documentation:
Update Kafka exporter README and Exporter README.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Chao (1b46cfd, 4dc35a3)

[codecov]

Codecov Report

Merging #2943 (aa39026) into main (90b2dec) will increase coverage by 0.01%.
The diff coverage is 95.74%.

@@            Coverage Diff             @@
##             main    #2943      +/-   ##
==========================================
+ Coverage   91.58%   91.59%   +0.01%     
==========================================
  Files         312      312              
  Lines       15351    15397      +46     
==========================================
+ Hits        14059    14103      +44     
- Misses        883      884       +1     
- Partials      409      410       +1     

Impacted Files	Coverage Δ
exporter/kafkaexporter/otlp_marshaller.go	60.00% <60.00%> (ø)
exporter/kafkaexporter/factory.go	100.00% <100.00%> (ø)
exporter/kafkaexporter/kafka_exporter.go	100.00% <100.00%> (ø)
exporter/kafkaexporter/marshaller.go	100.00% <100.00%> (ø)

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[bogdandrutu]

Add this to metrics as well :)